Alloy



Patented Oct. 26, 1937 PATENT OFFICE.

ALLOY Anthony (l; de Golyer, New York, N. Y.

No Drawing.

Application August 19, 1936 I Serial No. 96,779

3.0laims. (or. 14mm) The present invention relates to a new and usefulalloy and relates particularly to an alloy containing boron, tungsten,chromium and cobalt, which is characterized by being responsive tothermal treatment for the improvement of physical properties. l

'An object of the present invention is to provide an alloy especiallyadapted for use as metal cutting tools, the cutting efliciency of whichis superior to that of present known high speed steels and other alloys.A further object is to provide an alloy which is free from, or substantially free from carbon and which is readily amenable to thermaltreatment, by means of which the hardness, tensile strength; cuttingefllciency and other physical properties and characteristics may beaccurately controlled over a comparatively wide range.

I have found through experiment that by alloymg or otherwise intimatelycombining boron, tungsten, chromium and cobalt within the range of boron0.50% to 2.75%, tungsten 5% to chromium 1% to 15%, and cobaltsubstantially the balance, that I obtain metallic compositions 25 whichpossess in combination materially improved physical properties comparedto those .of heretofore known alloys or compositions intended forthe-cutting or working of metals, Alloys of this invention may be usedin .the cast condition but approximate maximum values of hardness,resistance to impact and certain jother important physical propertiescan be developed only through thermal treatment, or through mechanicalworking and subsequent thermal treatment. Bodies of the alloys whichhave been subjected to such treatment are particularly valuable for useas tools, dies and the like for the cutting or mechanical working ofmetals. g Numerous metallic compositions have heretofore been proposedas improvement on the generally known 18-4-4 type oftungsten-chromium-vanadium high speed tool steel, and while many of suchcompositions possess greater hardmass than such steel, all of them havedisadvantages which render them unsuitable for general application asmetal cutting or forming tools. Compositions containing principallycarbides of tungsten, molybdenum or tantalum bonded with a relativelysoft matrix metal have a high degree of. hardness, but are extremelybrittle. Cast compositions of the types heretofore-proposed require thepresence ofat least 1.50% carbon to qualify as metal cutting tools and,as is well known, such alloys are not only brittle, but are so sensitiveto various operating conditions as to greatly restrict the scope; ofusefulness. One of the greatest disadvantages of such heretoforeproposed compositions is that none of them are responsive to thermaltreatment for regulation 5 of physical properties, and consequentlyphysical properties and characteristics are governed entirely by thechemical composition of the sintered or cast material.

My alloy may be used in the as-cast condition, 10 or it may be forged orotherwise mechanically worked. I have found that both the cast andforged material are amenable to thermal treatment. For example, castbodies of this alloy may have a hardness of from 50 to on the Rock- 15well 0. scale and by subjecting'the material to suitable thermaltreatment, such as 'quenchingfrom a temperature higher thanapproximately 1000 C., the hardness may be lowered to an approximaterange of from 40 to'4'7 Rockwell C. 20 In this condition the bodies maybe ground, shaped or formed, as desired. The alloy may subsequently besubmitted to a second thermal treatment, such as heating to atemperature of less than 1000 C. for a period of one hour or 25 more, bywhich the hardness may be increased to from approximately 60 to RockwellC. In the latter condition the alloy is especially valuable for thecuttingor mechanical working of a. large number of metals and alloys, aswell as 30 numerous non-metallic materials. An important property'ofthis alloy is that virtually all of the maximum hardness, developed bythermal treatment, is retained when the alloy is subjectedto elevatedtemperatures, e. g.. such as are generated 35 in-the tip of a toolcutting metal at high speed. I

Although the alloy has a high degree of hardness and resistance toabrasion by hot metal chips, especially after thermal treatment, it isremarkably resistant .to failure from sudden or repeated 40 shock.Therefore, tools made of the present alloy retain an eflicient cuttingedge for longer periods than other. tools.

The more important distinctive and valuable advantages are, apparently,due tothe presence 45 of appreciable amounts of boron in thecompositlon, in conjunction with the other essential component elementswithin the percentages specified 4 herein.

I have found that molybdenum may be used to 50 supplant all or a portionof the tungsten of the present alloy. Likewise, uranium may be used inplace of either tungsten or molybdenum.

Specific examples of compositions within the.

scope of the present invention which I have found 55 well adapted formetal cutting tools, dies and the like are the following: boron 1.20%,tungsten 14%, chromium 5%, cobalt balance; boron 2.10%, tungsten 19.50%,chromium 4%, cobalt balance; boron 1.65%, molybdenum 13%, chromium 3.5%,cobalt balance; boron 1.70%, tungsten 5%, molybdenum 10%, chromium 8%,cobalt balance.

An objective of the present'invention is to provide alloys having highhardness, high resistance to shock and impact, advantageous metalcutting properties, etc., which are free or substantially free fromcarbon, and thus eliminate all of the serious disadvantages associatedwith carbon containing non-ferrous alloys or compositions intended. formetal cutting, tools. Although I prefer to have the alloys of thisinvention entirely free from carbon, in many instances I have foundcarbon present in the nature of an impurity incidental to manufacture.It is important to restrict the amount of carbon so present to a maximumof about 0.15%, as I have found that the .presence of higher percentagesof, this element make the alloy extremely brittle and subject to failureduring cutting operations, and, also inhibits the desired and necessaryreactions during thermal treatment. Furthermore, the presence ofappreciable amounts of carbon decreases the red hardness of thealloy, 1. e. hardness at temperatures of approximately 550 C. andhigher.

By reason of the fact that the elements forming the essential componentsof the alloy of the present invention invariably. are contaminated withother elements when produced in commercial quantities, the alloys of myinvention usually contain insignificant amounts of one or more elementsin the nature of impurities incidental to manufacture. The amount ofsuch impurities should be restricted to percentages which are noteffective on the physical properties or characteristics of the alloy,nor on the physical reactions during thermal treatment. I have foundthat the amount of any one of such in-- cidental impurities should berestricted to percentages not exceeding 1%, and in many instances tomaterially lower percentages. The presence of larger amounts of suchimpurities, particularly silicon and aluminum, materially decreases theresistance of the alloy to failure under shock and impact during cuttingoperations, and, further, inhibits the desired physical reactions duringthermal treatment. Therefore, the presence of effective amounts ofimpurities, such as carbon, silicon and aluminum, acts to appreciablylower the cutting efficiency and general value of the present alloy.

My investigations indicate that the preferred structure of a body of thepresent alloy, particularly after thermal treatment, comprises at leasttwo principal constituents: one, a relatively hard intermetalliccompoundof boron with one or more of the other essentialcomponents; and,second, a solid solution of two or more of the essential componentswhich has a lower degree of hardness and functions as a matrix. In someinstances the structure will contain a third constituent in the natureof an eutectoid. The ratio of the constituentaand the ratio of particlesize in any particular body of the alloy may be accurately controlledand fixed over a wide range by means of thermal treatment, or mechanicalworking and subsequent thermal treatment.

By reason of the combined advantageous physical properties possessed bythe alloy of the present invention, tools and other articles composed ofthis alloy may be operated efiiciently and economically under conditionswhich are impossible or uneconomic-a1 with tools or articles composed ofheretofore known alloys or metallic compositions.

By the term the balance substantially cobalt in the foregoing and in thefollowing claims, I intend that the alloy of the present inventioncomprises boron, chromium, and metal of the group tungsten, molybdenumand uranium within the percentage limits specified, with the remaindercobalt except for ineffective amounts of impurities'which may be presentincidental to manufacture.

I claim:

1. An age hardened alloy containing boron 0.50% to 2.75%, metal from thegroup tungsten, molybdenum and uranium 5% to 25%, chromium 1% to 15%,the balance substantially cobalt.

2. An age hardened alloy containing boron 0.50% to 2.75%, tungsten 5% to25%, chromium 1% to 15%, the balance substantially cobalt.

3. An age hardened alloy containing boron 0.50% to 2.75%, molybdenum 5%to 25%, chromium 1% to 15%, the balance substantially cobalt.

ANTHONY G. nu GOLYER.

